General F355 Q's

These might seem like very dumb questions but I ask only because I've heard many different answers, but I'm curious to know what experienced owners have to say...
How often do you change the oil filter on a F355, and what engine oil would you reccemend ?

On a seperate note:
Does anyone know what is the normal reading for the Bar gauge, on a manual F355?
Any troubleshooting tips if the heater (climate control) is not working?

I just installed the last part of my complete tubi exhaust set - the test pipes. Now I have the manifolds, test pipes, along with the stage III silencer. It sounds ok, but I keep getting the "slow down" warning on my dashboard. Anyone experiencing a similar issue ? Sorry for throwing ten million issues in one thread, just trying to speak my mind. And finally, Seasons greeting to everyone, and hope you are enjoying the holidays.